Technical Abstract:
Field and greenhouse experiments were conducted to compare the rates at which isolates of Soybean mosaic virus (SMV) were transmitted through seed. In the field experiment, six soybean plant introductions (PIs) were inoculated with eight SMV isolates, and six soybean PIs were inoculated with ten SMV isolates in the greenhouse. Transmission of SMV through seed ranged from 0 to 43% and 0% to 63% in seed from field- and greenhouse-grown plants, respectively. Differential transmission of SMV strains was observed. In addition, SMV isolate-by-cultivar interactions were seen in transmission rates. For example, SMV 88799 was transmitted from 43% of field-grown seed of PI 229324, but was not transmitted through seed of PIs 68522, 68671 or 86449. In contrast, SMV 413 was transmitted through seed from all PIs. SMV 1083 was highly transmitted (22 - 23%) in both field and greenhouse experiments. SMV G2 had very low seed transmission (0.0 - 0.4%) in both trials. Poorly-aphid transmissible SMV isolates that were maintained by mechanical inoculation were transmitted poorly through seed (2% from field seed and 6% from greenhouse seed). SMV isolates maintained by transmission by Aphis glycines were transmitted through seed at much higher rates (19% from field seed and 14% from greenhouse seed). This association between seed and aphid transmissibility suggests that the same regions of the SMV genome are involved in seed and aphid transmission.